A magnetic resonance imaging (MRI) apparatus corrects a transmit radio frequency (RF) magnetic field, in other words, performs B1 shimming, using a pair of B1 correction values (for example, B1 correction values for a phase and an amplitude of output of an RF amplifier related to a transmit RF wave), which are predetermined for each part to be imaged to correct non-uniformity of the transmit RF magnetic field (B1) due to a transmit RF wave.
When performing B1 shimming for an imaging target having high flexibility in positioning in the bore of the MRI apparatus, the position of the imaging target in the bore may vary from individual to individual. Since B1 shimming uses one type of correction value for each imaging target as described above, non-uniformity of B1 due to the position of the imaging target in the bore may not be completely corrected; as a result, brightness irregularity may occur in an MRI image.
B1 shimming may be performed using a spatial distribution of B1 obtained by pre-scanning performed before main scanning for each patient. However, from the viewpoint of avoiding extending the time required for imaging, it is not preferable to perform pre-scanning for the purpose of obtaining a spatial distribution of B1.
An objective is to perform B1 shimming appropriately for an imaging target placed in the bore.